Disable XR browser tests on RX 550

Disables the XR browser tests on the RX 550 tester, as the tests
randomly hang indefinitely on this hardware configuration.

[email protected]

Bug: 1018896
Change-Id: Ie874c7df846d5133cd91fcf03eb7592e4c2b1347
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1884278
Reviewed-by: Brian Sheedy <[email protected]>
Reviewed-by: Yuly Novikov <[email protected]>
Commit-Queue: Brian Sheedy <[email protected]>
Cr-Commit-Position: refs/heads/master@{#710145}
diff --git a/testing/buildbot/test_suite_exceptions.pyl b/testing/buildbot/test_suite_exceptions.pyl
index 39427d650..b145b12 100644
--- a/testing/buildbot/test_suite_exceptions.pyl
+++ b/testing/buildbot/test_suite_exceptions.pyl
@@ -2133,6 +2133,8 @@
       'Win7 FYI Debug (AMD)',
       # Fails on the bot, http://crbug.com/868143
       'Win7 FYI Release (AMD)',
+      # Randomly hangs indefinitely https://crbug.com/1018896.
+      'Win10 FYI x64 Release (AMD RX 550)',
     ],
   },
 }